switch
A switch statement is a shorter way to write a sequence of if - else statements. It runs the first case whose value is equal to the condition expression.
Go’s switch is like the one in C, C++, Java, JavaScript, and PHP, except that Go only runs the selected case, not all the cases that follow. In effect, the break statement that is needed at the end of each case in those languages is provided automatically in Go. Another important difference is that Go’s switch cases need not be constants, and the values involved need not be integers.
With Defaults
package main
import (
"fmt"
"runtime"
)
func main() {
fmt.Print("Go runs on ")
switch os := runtime.GOOS; os {
case "darwin":
fmt.Println("OS X.")
case "linux":
fmt.Println("Linux.")
default:
// freebsd, openbsd,
// plan9, windows...
fmt.Printf("%s.\n", os)
}
}
Multiple expressions in the same case statement
package main
import (
"fmt"
"runtime"
)
func main() {
switch time.Now().Weekday() {
case time.Saturday, time.Sunday:
fmt.Println("It's the weekend")
default:
fmt.Println("It's a weekday")
}
}
As if
switch without an expression is an alternate way to express if/else logic. Here we also show how the case expressions can be non-constants.
t := time.Now()
switch {
case t.Hour() < 12:
fmt.Println("It's before noon")
default:
fmt.Println("It's after noon")
}
Check Types
A type switch compares types instead of values. You can use this to discover the type of an interface value. In this example, the variable t will have the type corresponding to its clause.
whatAmI := func(i interface{}) {
switch t := i.(type) {
case bool:
fmt.Println("I'm a bool")
case int:
fmt.Println("I'm an int")
default:
fmt.Printf("Don't know type %T\n", t)
}
}